1. Field of the Invention
The present invention relates to a three-dimensional driving system for a transfer feeder of a transfer press for feeding works into successive processing stations that are individually surrounded by a plurality of uprights.
2. Description of the Related Art:
In an automatic press system, a transfer press has conventionally been equipped with a servo-assisted three-dimensional driving system for a transfer feeder that is driven by servomotors. To feed works into processing stations of the transfer press, the three-dimensional driving system comprises a pair of transfer bars arranged parallel to the feed direction of the works, a feed mechanism provided at one end of the transfer bars, and clamp and lift mechanisms provided closer the other end of the transfer bars. As the transfer bars are caused to move in the feed direction by the feed mechanism and to move in lifting and clamping directions by the clamp and lift mechanisms, the transfer bars grip and release each work between themselves to thereby carry the works into and out of dies of successive stages of a press process automatically.
If it is desired to successively feed a series of works from one die location to the next along a line of processing stations for sequential processing, for example, the clamp and lift mechanisms are provided between successive uprights or between the successive die locations of the transfer press, and individual sections of the feed, clamp and lift mechanisms are driven in three-dimensional directions in a controlled manner, so that each work is automatically processed by the transfer press through a sequence of steps.
A related art example of a servo-assisted three-dimensional driving system for a transfer feeder is disclosed in JP-B-2-1 1934U. Since servomotors are directly connected to individual mechanisms including a feed mechanism, clamp mechanisms and lift mechanisms in this servo-assisted three-dimensional driving system, it is possible to move transfer bars at high speeds in a three-dimensional space and thereby achieve an improvement in productivity.
Another example of the related art is a three-dimensional driving system for a mechanical transfer feeder that is driven by motive power supplied from a drive system of a press. This mechanical three-dimensional driving system takes the motive power from the drive system of the press through transmission mechanisms, which include a bevel gear mechanism, pinions and cam shafts. Therefore, when installing a servo-assisted three-dimensional driving system instead of the existing mechanical three-dimensional driving system, an extra installation space that has not been required will become necessary, and mounting sites for individual servomotors will pose a serious problem. Especially when a press process involves many stages and feed lengths of transfer bars are short, the distances between successive uprights become small and, therefore, great limitations will be imposed on the availability of mounting sites for the servomotors.
It is necessary to install individual servomotors so that they would not interfere with the main structure and dies of the transfer press. Furthermore, although large-sized servomotors having a large capacity are required, it is practically impossible to install the large-sized servomotors for reasons stated above. Therefore, it has conventionally been necessary to install a number of small-sized servomotors.